LeetCode--No.112--Path Sum

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Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5             / \            4   8           /   / \          11  13  4         /  \      \        7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

思路：

递归：

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean hasPathSum(TreeNode root, int sum) {        if (root == null)   return false;        else    return equal(root, sum);    }    public boolean equal (TreeNode node, int sum){        if (node.left == null && node.right == null){            if(node.val == sum) return true;            else    return false;        }        else if (node.left == null){            if (equal(node.right, sum-node.val))    return true;            else    return false;        }        else if(node.right == null){            if (equal(node.left, sum-node.val))     return true;            else    return false;        }        else{            if (equal(node.left, sum-node.val) || equal(node.right, sum-node.val))  return true;            else    return false;        }    }}

只是。。。这TM也叫代码？！！这么恶心？！！这是我写的？！！食屎去吧！！！！

public class Solution {    public boolean hasPathSum(TreeNode root, int sum) {        if (root == null)               return false;        if (root.left == null && root.right == null && root.val == sum)            return true;        return hasPathSum(root.left, sum-root.val) || hasPathSum(root.right, sum-root.val);    }}

这才叫代码好嘛！

非递归（队列）解法：

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean hasPathSum(TreeNode root, int sum) {        if (root == null)               return false;        LinkedList<TreeNode> nodes = new LinkedList<TreeNode>();        LinkedList<Integer> values = new LinkedList<Integer>();                nodes.add(root);        values.add(root.val);                while(!nodes.isEmpty()){            TreeNode curr = nodes.poll();            int sumValue = values.poll();            if(curr.left == null && curr.right == null && sumValue == sum)                return true;            if(curr.left != null){                nodes.add(curr.left);                values.add(sumValue + curr.left.val);            }            if(curr.right != null){                nodes.add(curr.right);                values.add(sumValue + curr.right.val);            }        }        return false;    }}

代码来自：http://www.programcreek.com/2013/01/leetcode-path-sum/

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